Hot Swappable Uninterruptible
Power Supplies
Removing the Downtime in Data Centers
White Paper
www.xpcc.com | © 2015 Xtreme Power Conversion Corporation. All rights reserved. (Rev 1/12/15)
Hot Swappable Uninterruptible Power Supplies
White Paper
Introduction
Unscheduled downtime of critical loads can cause a tremendous financial loss while frustrating IT technicians, and
management. Many Uninterruptible Power Supplies (UPS) have addressed the down time associated with routine
battery maintenance by offering a “hot swappable battery” feature integral to their UPS design. This well known
feature is often a key consideration for many buyers when sourcing a UPS. However, this feature falls short when
protecting against downtimes associated with other UPS emergency and planned maintenance activities. These
more important potential problems affecting downtime can be easily overlooked without the proper power distribution considerations.
In today’s cost sensitive environment, it is critical to avoid any preventable downtimes associated with UPS failures
as well as routine UPS maintenance. This paper will outline the advantages of the bypass distribution module
as the solution to unscheduled downtime as well as illustrate how the IT professional can essentially have a “hot
swappable UPS” when adding this device into the power distribution network.
The Problem
A typical single phase power distribution scenario is shown below in figure 1. Several types of faults can occur requiring the UPS to be shutdown, replaced, or repaired. When these types of faults occur, the user is forced to shut
down the connected loads while the repairs are made or the UPS is replaced. The loads can be manually restarted
on utility during this time but are typically not protected from a power loss.
Figure 1
Preventative maintenance can also require the loads to be secured from the UPS. For example, a UPS without the
“hot swappable battery” feature would require the loads to be shutdown while the batteries are replaced. This
often generates additional expenditures due to inconvenient out-of-hours maintenance windows.
The Solution
A bypass module added to the power distribution network alleviates unscheduled downtime by allowing the user
to select between multiple sources of power for the connected loads. Sources are typically Utility Power and UPS
power. Should there be a fault requiring maintenance or a planned maintenance activity on the UPS, the user can
follow a simple procedure to isolate the load from the affected source.
Figure 2
Xtreme Advantage:
Key product features should be considered when selecting a bypass module. For example, Xtreme Power’s series
of XBDM’s (Xtreme Bypass Distribution Module) prevent unnecessary downtime for the connected loads but also
provide the additional key advantages:
1. XBDM’s can be used with almost any UPS manufacturer for UPS sizes up to 3kVA
2. Provides additional receptacles for load distribution
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3. Provides additional surge protection for connected loads
4. Can be added to the distribution network at any time
Coupling the inherent advantages of bypass module technology with the design considerations made by Xtreme
Power has allowed this series of product to stand alone in this area of power products.
Typical Xtreme Power XBDM Module (Front View)
Typical Xtreme Power XBDM Module (Rear View)
The XBDMs can be mounted in the front or rear of a 19” rack, or vertical in the front or rear of a 19” rack, or
mounted to a wall near the UPS and equipment to be support. Flexible configuration allows for the placement of
the XBDM where it is needed.
How the XBDM works:
Utility Power is connected to the XBDM. The XBDM provides the input power to the UPS and the output of the UPS
is fed back into the XBDM. The critical loads are connected directly to the XBDM’s receptacles.
There are two modes of operation for the XBDM: Utility and UPS.
• UPS Mode: Power is being routed through the UPS system during normal operation
Figure 3: UPS MODE
• Utility mode: Power bypasses the UPS system; XBDM supplies power to the load. The UPS can be removed and replaced without any interference to the load.
Figure 4: UTILITY MODE
• Transferring between the two modes is accomplished via a break-before-make, UL 489 listed, rocker switch
that insures a transfer of 8ms or less between sources. A typical transfer is shown in figure 5.
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Figure 5: 4.2ms TRANSFER TIME
Conclusion
Unscheduled downtime associated with single phase UPS maintenance, and emergency maintenance has long
been a battle for IT Personnel. UPS manufacturers have tried to limit the downtime linked to battery replacements
by incorporating a well known feature as “hot swappable batteries” but this does not provide enough protection
for other types of downtime. The bypass module has proved to be a valuable power product by virtually removing
almost all of the unscheduled downtimes. Bypass modules such as Xtreme Power’s XBDM should be considered
when sourcing a UPS and for modifying an existing power distribution network.
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Hot Swappable Uninterruptible Power Supplies
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About Xtreme Power Conversion Corporation
Xtreme Power is a global manufacturer of power quality and data center solutions. Xtreme Power manufactures
UPS from 400VA to 40kVA. We design, engineer, and services UPS, rack power distribution units, and portable
cooling products for a global network of OEMs and distributors.
This white paper is authored by:
Mike Conlon
Director of Technology
Xtreme Power Conversion Corporation – U.S.
230 Yuma Street
Denver, CO 80223
Tel (800) 582-4524
www.xpcc.com
Xtreme Power Conversion Corporation – EMEA
Rotterdam, NL
emea@xpcc.com
Xtreme Power Conversion Corporation
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